bʊl.ɪtpɹuːf ˌʌnəˈseɪləbl̩ ˈwɔː.tə.taɪt without flaws or loopholes an ironclad contract a watertight alibi a bulletproof argument inflexibly entrenched and unchangeable brassbound traditions brassbound party loyalists an ironclad rule sheathed in iron plates for protection a wooden warship of the 19th century that is plated with iron or steel armor